1. Field of the Invention
The present invention relates to a material sheet for a metal sintered body and a method for manufacturing the same and a method for manufacturing a metal sintered body.
2. Description of the Prior Art
In the past, where a metal sintered body is manufactured, there has been proposed a method, in order to carry out molding operation thereof, which comprises using a plasticizing material wherein a metal powder having a sintering property and a plastic binder are kneaded, molding the plasticizing material into a predetermined configuration, subjecting the plastic binder in a molded body to thermal decompostion and sintering the metal powder.
In the aforesaid method, the sintered body gives rise to a change in size due to expansion unless some back-up means is taken when the metal powder is sintered, and a deviation of nearly 4% before and after sintering possibly occurs.
As the metal powder having a sintering property, a self-fluxing alloy powder, for example, Ni self-fluxing alloy metal powder of Ni-B-Si family. However, the solid phase line of this alloy is 1010.degree.-1020.degree. C. and the liquid phase line thereof is 1075.degree. to 1085.degree.C. When sintering is effected at a zone of lower temperature than the solid phase line, a contour maintaining property is good but a sintering strength is low whereas when sintering is effected at a zone of higher temperature than the liquid phase line, all powders become molten and flow, as a result of which the contour maintaining property is worsened.
In view of the foregoing, sintering is effected at a suitable temperature between the solid phase line and the liquid phase line, for example, at a temperature in the vicinity of 1050.degree. C.
However, in the case where sintering is effected at the above-described temperature, the sintered body shows a change in size due to shrinkage, deteriorating accuracy in size and the sintering strength is not so high.
Further, there has been proposed a method in which the aforesaid plasticizing material is formed into a sheet to prepare a material sheet, which sheet is used to obtain a metal sintered body. In this case, however, a stacking property of the material sheet is deteriorated depending on quality of the plastic binder and therefore there poses problems in that peeling between layers of the molded body occurs and cracks occur.